Method of drying rayon thread by high-frequency electric currents



Jan. 6, 1948. F. H. GRIFFIN' I 2,433,342

METHOD OF DRYING RAYON THREADBY HIGH-FREQUENCY ELECTRIC CURRENTS Filed Feb 16, 1944 RADIO mrouzucy use/Arm Jul ma.-

Patented Jan. 6, 1948 METHOD OF DRYING RAYON THREAD BY HIGH-FREQUENCY ELECTRIC CURRENTS Frank H. Grifiin, Wawa, Pa., assignor to American Viscose Corporation, Wilmington, Dcl., a corporation oi Delaware Application February 16, 1944, Serial No. 522,550

This invention relates to an improved method of producing artificial filamentary material. More particularly, the invention is concerned with methods of drying artificial filamentary material, especially continuously travelling artificial filements which have been freshly spun, under uniform heat conditions, and under a constant tension which permits substantially free and uniform shrinkage of the filamentary material during drying.

In the usual processes oi manufacturing artificial filaments and the like, the filaments are collected in the form of a wound package, such as a hollow perforated tube in bobbin spinning, or in the form of an annular winding in a centrifugal spinning bucket. The filamentary material on the wound packages is then subjected to the usual wet after-treating processes, and subsequently dried by circulating hot air through and about the packages.

During such drying, the material constituting the inner convolutions of the package dry at a different rate of speed than the material constituting the outer convolutions, with the result that the inner layers do not shrink to the same extent as the outer layers. Knitted, woven, or otherwise fabricated materials manufactured from filamentary material which has been dried while in the form of wound packages are fre-' quently found to possess varying residual shrinkage capacities and dyeing afinities, thus rendering them objectionable to the textile trade.

The present application is concerned with an improved method of drying moist or re-moistened filamentary material, wherein all of the material is dried at a uniform rate of speed and under conditions of tension which permit free shrinkage or contraction of the filamentary material during drying, such shrinkage being uniform throughout the entire length of the filamentary material.

The method of drying according to my invention may be advantageously applied to the drying of artificial filaments prepared according to the viscose process. In that process, the viscose is extruded into a coagulating and regenerating bath containing sulfuric acid and other constituents, after which they are withdrawn from the bath and washed free of the acid and other adhering substances, with or without simultaneous stretching.

In accordance with my invention, such filamentary material containing water remaining after removing from the material injurious acids or other foreign substances, is uniformly dried and permitted to shrink freely during drying,

3 Claims. (Cl. 34-1) ill by subjecting it, preferably in the form of a bundle of filaments, twisted or untwisted, such as yarns or threads, to a high frequency electric current, while maintaining the filamentary material under a light but constant tension which may be created by the weight of the material it. self. The high frequency electric current is induced within the filamentary material longitudinally thereof such as by passing the filamentary material downwardly and concentrically through a series of electrodes preferably equidistantly spaced from one another in an enclosed chamber. The degree'of tension applied to the filamentary material is as near the zero point as possible, only the tension of a short length of filamentary material suspended through and in the vicinity of the electrodes being present.

The invention will be more fully understood by reference to the accompanying drawing, in which Figure 1 shows a preferred apparatus which may be utilized in practicing my invention;

Figure 2 shows a modification; and

Figure 3 is a transverse cross-sectional View of the preferred form of electrode.

As illustrated in Figure l viscose or the like is extruded through the orifices 01? spinneret i into spinning bath 2, and. the filaments 3 thus formed are drawn through and from the bath by godet d from which they pass to godet 5, which may be rotated at a difierent peripheral speed from godet l in order to stretch the filaments. From godet ii the water-laden filamentary material is passed over feed roll l and then passed generally concentrically through a set of three electrodes 8, ii and ill, which are preferably of U-shape, and which are attached by means of brackets ii, iii and 53 respectively, to the inside wall of the chamber it. The two outer electrodes ii and it. may be grounded directly to serve as a guard to prevent current flowing in the filaments beyond the electrodes. The middle electrode a is connected by a suitable electrical conductor iii to one pole it of any suitable source ll of high irequency electric current, such as a radio frequency oscillator. The other pole iii of the high frequency oscillator is grounded at it. The oscillator ll may be connected to a suitable source of power by th conductors 20 and 2 l. During their passage between godets 4 and 5, thefilaments may be subjected to a spray of water from nozzle 6 for the purpose of at least partially washing off the acid or other corrosive materials clinging thereto, so that no charring or other deleterious eifects upon the filament are caused by the high temperatures induced in the filaments by the oscillator. Additional washing, or the entire washing, may be performed on the godets 5 and l, or as the filamentary bundle travels to, from, or between them. The removal of foreign substances may be effected by treatment of the filaments with other liquids than water where appropriate, and, if desired, bleaching may be performed immediately after washing, prior topassage of the filamentary material through the electrodes of the oscillator. Regardless of the specific manner or stage of washing, it is essential for the purposes of my invention to remove substantially all of the acid or any other substances which would injure the filamentary material at elevated temperatures prior to the passage thereof through the electrodes 8, 9 and ll! of the drying device.

After passing downwardly through the electrodes 8, 9 and i0, and out of chamber H, the filamentary material is permitted to form a loop 22, so that the only tension exerted thereon is that which is due to the weight of the filamentary material itself, thus permitting free shrinkage of the filaments during drying. A thread brake 23 may be provided for the purpose of forming loop 22. The dried filamentary material is then directed over suitable thread-handling means such as feed rollers 24, to any suitable windup and/or twisting device (not shown).

A thread guide or a plurality of such guides composed of a suitable insulating material such as porcelain, glass, or the like, may be provided at any point along the course of travel of the filamentary material from feed roll I through the electrodes in the chamber H, to assist in maintaining the filamentary bundle generally concentrically within the electrodes.

Referring now to the arrangement shown in Figure 2,. in which the apparatus is essentially the same as shown in Figure 1 except that a system of two electrodes spaced horizontally with respect to each other is utilized, the filamentary material 3 is passed between feed rollers 25, through electrode 23, over guide roller 21, through electrode 26, and finally through feed rollers 29, after which i rollers 25 revolve is suitably adjusted, and means comprising a light weight 30 is provided for forming the material into a loop 32, after it leaves electrode 26 and passes over guide 31.

The arrangement shown in Figures 1 and 2 constitutes essentially a capacitive coupling of the high frequency oscillator H to the traveling filamentary bundle 3. The spacing of the electrodes may be varied, if necessary or desirable, but in general for uniformly drying water-laden filamentary material which is free of injurious acids or the like, the equidistant spacing of the successive pairs of electrodes is entirely satisfactory.

The electrodes may be of any suitable shape. Those shown in Figure 3 of the drawing are of U-shape and are preferred from the standpoint of lacing up the device. The electrodes are provided with a coating of insulating material such as glass.

Any high frequency oscillator may be employed,

' an oscillator producing currents in the range of radio frequencies being preferred. For example, an oscillator producing a current having a frequency of the order of five to six megacycles up to 25 to 60 megacycles or so, and operating at a 4 of the filaments comprising a filamentary bundie and throughout the entire length thereof.

The method of drying in accordance with my invention may be applied to artificial moist or remolstened filamentary material of all kinds, such as filaments obtained from viscose, cuprammonium cellulose, vinyl resins, especially vinylacetate-chloride copolymers, cellulose acetate, ethyl cellulose, nylon, and proteinous materials such as casein. The drying method may also be applied to natural filamentary material such as tows or yarns made of or comprising cotton, wool and silk.

While a preferred embodiment of the invention has been shown, it will be apparent that changes and variations may be made therein.

I claim:

1. In the art of manufacturing rayon thread, the step comprising subjecting running lengths of moist filamentary material to a high frequency electric current induced longitudinally thereof, under a uniform tension created only by the weight of the filamentary material to thereby permit substantially free and uniform shrinkage thereof during drying.

2. The method of drying filamentary material which comprises passing moist filamentary material longitudinally downwardly along a predetermined path, generating in an oscillatory circuit which has terminals at spaced points in said path a high frequency electric current, passing said filamentary material through said terminals in capacitive relation thereto, whereby to generate in the portion of said filamentary material between said terminals an alternating current flowing through said filamentary material alternately in the direction of travel thereof and then in the opposite direction for drying said portion, said filamentary material passing along said predetermined path under a uniform tension created only by the weight of the filamentary material to thereby permit substantially free and uniform shrinkage thereof during drying,

3. The method of drying filamentary material comprising subjecting running lengths of moist filamentary material to a high frequency electric current induced longitudinally thereof, under a. uniform tension created only by the weight of the filamentary material to thereby permit substanvoltage from 1,000 to 50,000 volts, a voltage of tially free and uniform shrinkage thereof during rying.

FRANK H. GRIFFIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

